Since polyester resins including polybutylene terephthalate have excellent mechanical properties, heat resistance, chemical resistance and the like, they are widely used as a molded product for application in electric and electronic fields, automobile field and the like.
Many of these applications require flame retardancy, and resins are available that are provided with flame retardancy by using mainly a halogen compound and an antimony compound as a flame retardant or a flame retardant aid.
However, the decomposed product of a halogen flame retardant may corrode a metal which forms an electric part, and some halogen flame retardants have a problem with the influence on environment. Therefore, non-halogen flame retardant resins are desired.
The non-halogen flame retardants include phosphorus compounds, for example. As typical organic phosphorus compounds, low-molecular-weight phosphates such as triphenyl phosphate (TPP) have been frequently used. However, a polyester resin such as polybutylene terephthalate has relatively high processing temperature, and encounters problems in bleedout and heat resistance when a low-molecular-weight phosphate is used.
JP-A 7-126498 discloses a non-halogen flame retardant for a polyester resin, which is prepared by melt-reacting a polyester resin, an epoxy compound having at least two epoxy groups in the molecule, a phenol resin and/or at least one non-halogen flame retardant compound selected from phosphorus, nitrogen and boron compounds having a functional group capable of reacting with an epoxy group.
JP-A 7-278267 discloses a flame-retardant polyester resin composition comprising 5 to 50 parts by weight of the above non-halogen flame retardant and 100 parts by weight of a polyester resin.
The above non-halogen flame retardant has a characteristic feature in that it comprises an epoxy compound having at least two epoxy groups in the molecule.
JP-A 8-188717 discloses a flame retardant resin composition comprising a thermoplastic resin such as polystyrene or polyester, a phosphorus compound such as a phosphate or phosphite, and a phenol aralkyl resin such as a reaction product between a phenol (such as cresol) and an aralkyl halide (such as .alpha.,.alpha.-dichloro-p-xylene).
JP-A 8-208884 discloses a flame retardant resin composition comprising a thermoplastic resin such as polystyrene or polyester, a phosphorus compound such as a phosphate or phosphite, and a phenol resin derived from a phenol substituted at the ortho- or para-position.
Meanwhile, Journal of Fire Retardant Chemistry vol. 7, pp. 69-76, 1980 discloses that polystyrene can be made flame-retardant by red phosphorus and a phenol resin.
JP-A 2-37370 discloses a flame retardant polyester resin composition comprising 99 to 34 parts by weight of a thermoplastic polyester resin having a softening point of 150.degree. C. or higher such as polyethylene terephthalate, 1 to 25 parts by weight of red phosphorus coated with a thermosetting resin, and 10 to 55 parts by weight of a reinforcing filler.